Who's idea of 30? What I think a 30 year old looks like and what anyone else does is going to differ drastically.

"Apply again" - don't they keep track of fingerprints and other biometrics?

how convincing does this need to be? is it in person, over video call?

As a thirty year old, all I need to do is shave regularly and I look to be in my mid to early 20s. In the U.S. there is a minor amount of Pride in how late in age you're "carded" when you buy alcoholic drinks. That is, the sales person requests to see ID because he/she is concerned you might not be 21 years or older. I've known people in their late 30s and even 40s who get carded.

What sort of basis are they using to 'test' age? - I lost a lot of hair early in life, and so got waved through at bars in University when some of the professors I was with got carded. Over a decade later and a rise in popularity of beards, I'm now getting carded...

@hszmv I've known 13 year olds who don't.

@Ash I had a buddy who was going grey in high school. Age is just a number, as they say.

@Alexander let's assume they do but Sam can influence authorities ; what Sam can't do is to influence how others see him so if he doesn't fake his appearance somehow - many people will start asking questions

Since the answer is, as long as he wants to. I feel this question is too opinion based.

@TrevorD I disagree. It is limited to an objective factor: how long will the tech allow him to stay visually young. The tech is also well-defined: it is that what we have at our disposal in our present day. And that is the essence of the question.

@AlmaDo But visually doesn't make much sense. Looking old and being old don't have the connection people assume they have. I had a 25 year old friend that was literally the size of a baby because his bones were too brittle, so would he not be allowed in? I have another friend that turned grey when he was 18. My own father lost most of his hair by the time he was 20. Without knowing the visual traits this group requires to be considered the right age, I am not sure how we can answer this.

Your fourth bullet doesn't work as you have it written, because the surrounding people AREN'T going to be new, unless he leaves the class for at least five years. E.g. if Sam enters at 25, when he leaves at 30, there's going to be a bunch of people who just joined, people who have only been there for a year, people who have only been there for two years, etc. So he either has to come back with a new identity AND a new face so he can't be recognized (which solves the age problem too), or he has to wait five years before he comes back (which makes the age problem worse).

@MorrisTheCat it's a good point. I have to remind myself that what I have in mind and what is written is not the same. Added better clarification (e.g. exposure only within the group, no newcomers to the groups that were already formed)

@AlmaDo the real question is how much time does 'Sam' have to spend PHYSICALLY face to face with these people. If it's just VR sims and telepresence and all that kind of thing, then it's a VERY different problem than if he has to spend four or five hours a day around other people who might notice something amiss.

@MorrisTheCat regular setting, face to face exposure daily for potentially several hours. I think I need to add that too. It looks like I'm not great with filling in important details, sorry.

@AlmaDo am I correctly following from your earlier comment that Sam is only associating with people in the privileged class that joined at the SAME TIME he did? e.g. it's like being in High School, you don't associate with people in senior or junior years?

@MorrisTheCat correct. For simplicity: not only does he not associate with other groups (because to avoid being discovered), he also can not do this physically (because of the limitations of the job he does). There is no way Sam will be exposed to anyone but his current group and that exposure group will stay the same as it was when everyone joined during next 5 years.

I hate to be the party-pooper, but this does appear to be about a story set within a world and not about worldbuilding and is as-such off topic. Voting to close as too story-based.

@Confoundedbybeigefish.I don't follow your argument. I had to provide great level of detail because people asked (and that made sense). The question is about the very concrete thing that is not related to any story. I have only one thing from the "Story" - the name "Sam" (which doesn't happen to be the one I use).

Sam is an idiot. He loses his contacts every couple years. He resets his network every time he reapplies. Instead, if he does favors for people in the class and builds his network permanently, he can get WAAAY more benefits than he ever could by staying in the class.

@Alma Do - then you need to make it clear that this privileged group is NOT the authority. They more like "platinum members" of some sort. They enjoy privileges, but won't set rules and scrutinize their membership themselves. If any member rises the question, authorities would simply say: "Calm down, this guy is good."